1. Field of the Invention
This invention pertains generally to eddy current data obtained from the nondestructive examination of a component and, more particularly, to a method of synthesizing eddy current data to be used for training data analysts and/or testing inspection techniques.
2. Related Art
Nondestructive examination of components is carried out in a number of fields and is particularly important in the periodic inspection of steam generator tubing that forms part of the primary circuit of a pressurized water reactor nuclear steam supply system. The integrity of the steam generator tubing in the primary circuit of a pressurized water nuclear reactor steam supply system is essential to assure that radioactive coolant from the reactor does not contaminate the secondary side circuit in which it is in heat transfer relationship to create steam to drive a turbine which in turn drives a generator to create electricity. The hot leg of the nuclear reactor coolant loop is connected to one side of a hemispherical plenum on the under side of the steam generator. The hemispherical plenum is divided into two substantially equal parts and bounded on its upper side by a tube sheet. The heat exchanger tubes extend from one side of the hemispherical plenum through the tube sheet into the secondary side in a U-shaped design that terminates through the tube sheet to the other side of the hemispherical plenum. The other side of the hemispherical plenum is connected to a cold leg of the nuclear reactor coolant loop. There are hundreds of tubes within the steam generator communicating between the hot side and the cold side of the plenum. To ensure the integrity of the tubes, periodically, during reactor outages, the plenum is accessed through manways and the tubes inspected. Eddy current probes are inserted into the tubes and the tube position and data read by the eddy current detectors are recorded to identify any flaws that may have developed in the tubes during the preceding service period between inspections. The eddy current data takes the form of signal patterns, which require a great deal of experience to interpret to identify the existence, type and extent of any flaws that may be present in the tubing. If flaws are detected that exceed a given criteria, the corresponding tubing is plugged and thus taken out of service to reduce the likelihood of failure during the forthcoming reactor operating cycle.
Obtaining eddy current data representative of the various kinds of flaws that are likely to be encountered under field conditions, among a background of scattering data and other noise encountered in the field, to train data analysts and test inspection techniques, is extremely difficult and expensive. However, such training is essential to being able to properly interpret eddy current data. Similarly, the testing of inspection techniques is necessary to understand the probability of detecting different types of flaws and the affect the sizing of a flaw has on the various discontinuity responses.
Accordingly, it is an object of this invention to provide eddy current data representative of the detection of a number of different flaws that is suitable for training and qualifying analysts and testing inspection techniques.
It is a further object of this invention to provide such eddy current data with substantially the same background, scatter and other noise as is encountered in the field.
Additionally, it is an object of this invention to provide such eddy current data in a relatively inexpensive manner.
These and other objects are achieved by the method of this invention for synthesizing eddy current data to be used for training data analysts and/or testing inspection techniques. In the preferred embodiment, the steps of the method of this invention create a specimen that simulates the component undergoing nondestructive examination with preselected flaws of interest. The specimen is then monitored by an eddy current probe to create a set of eddy current data representative of the flaws detected in the specimen. At least some of the eddy current data collected at a field site is combined with at least some of the eddy current data collected from the specimen to establish a combined data train that reflects the eddy current response to the selected flaws in a background representative of data collected at the field site.
Preferably, the eddy current probes used to collect data at the field site and at the specimen are of the same type and are operated at the same inspection frequencies and data sampling rates. Additionally, in the preferred embodiment, both the field and specimen data sets are calibrated separately to substantially the same standard so that the signal level and orientation for a given flaw correspond. Prior to inserting the data obtained from the field into the specimen data or the specimen data into the data obtained from the field, the data to be inserted is arithmetically operated on to adjust the calibration, so when inserted, the inserted data has the same calibration factor as the data in which it is being inserted so that the combined set of data forms a new integrated data set that is separately stored. In another embodiment of this invention, the specimen could be replaced by a mathematical model and the data obtained from the specimen could be generated by the mathematical model.